It’s not clear how long Sen. Edward M. Kennedy will be away from the Senate, but his absence is already having an impact on pending legislation.

First elected to the Senate in 1962, Kennedy is an indispensable deal maker and one of the chamber’s most skilled legislators. He is also the chairman of the Senate Health, Education, Labor and Pensions Committee, where legislation will inevitably languish without a Senate giant on hand to negotiate deals.

With the 76-year-old Massachusetts senator in the hospital since Saturday, a major labor union bill for public safety workers is on the back burner, a higher education bill has been sidelined and a handful of routine health care bills are on hold.

In addition, Kennedy’s absence — when coupled with the frequent absences of Democratic presidential candidates and fellow Sens. Barack Obama of Illinois and Hillary Rodham Clinton of New York — may cause problems for Senate Democrats on close, party-line floor votes such as those to come on the Iraq war funding bill.

Senate leaders said it was too soon to discuss if or when any other senator would step in to run Kennedy’s committee, because it’s not clear whether he’ll be hospitalized for just a few days or much longer. Kennedy’s doctors have not yet said how they’ll treat the brain tumor that caused him to suffer a seizure in Hyannisport, Mass., on Saturday.

Kennedy has served as chairman of the HELP committee since the Democratic takeover in November 2006, using the post to push through a wide variety of bills he supports.

Although Senate Democrats operate under a strict seniority system, the party also generally prohibits a senator from heading more than one committee at a time.

Next in line behind Kennedy on the HELP panel is Sen. Chris Dodd (D-Conn.), who is unlikely to give up his chairmanship of the Banking, Housing and Urban Affairs Committee. Sen. Tom Harkin (D-Iowa), third in line on the HELP committee, wields the gavel at the Agriculture, Nutrition and Forestry Committee. With the authorization of the new, five-year Farm Bill just wrapping up — it has passed the House and Senate with veto-proof majorities, despite opposition from President Bush — Harkin could conceivably assert his right to take over the HELP panel.

If he doesn’t, the committee’s chairmanship could fall, in Kennedy’s absence, to Sen. Barbara Mikulski (D-Md.), the fourth-ranking Democrat on the panel.

Mikulski already is a senior member of the powerful Appropriations Committee, and she has used that seat to steer hundreds of millions in federal tax dollars to her home state. Mikulski could retain her Appropriations seat while heading the HELP committee.

However long Kennedy is gone, senators said Tuesday that the Senate will be worse off without him. Having spent 46 years in the body, Kennedy provides an institutional presence that carries weight on both sides of the aisle. When working the Senate floor, he has the ability to give a rousing stemwinder of a speech criticizing Republicans, then, moments later, make concessions and find middle ground to move major bills.

“Ted is appropriately known for his legendary legislative abilities and as a phenomenal leader,” said Sen. Olympia Snowe (R-Maine).

Although he is an icon of the left, Kennedy is well-known for cutting the deal with Bush that produced No Child Left Behind, and he was one of Arizona Republican Sen. John McCain’s primary partners on last year’s failed immigration legislation.

On some Senate committees, the Democratic chairman and the ranking Republican are polar opposites who clash, yet Kennedy works closely with conservative Wyoming Sen. Michael B. Enzi, who says Kennedy is always fair to the minority party.

“We keep him in our prayers and hope for a speedy recovery,” Enzi said Tuesday. “I enjoy working with him. We are actually a pretty productive team. We have a lot of bills in the works; we usually do about one bill a month. He will be in my prayers.”

Just last week, Kennedy skillfully roamed the Senate floor, managing legislation that would extend collective bargaining rights to first responders such as firefighters and rescue crews. Kennedy handled a series of amendments, and the bill was still the pending business on the Senate floor when Kennedy headed to Cape Cod, Mass., for the weekend.

The bill is a top priority for public safety workers because it would give first responders the right to unionize in any municipality larger than 5,000 people. In Kennedy’s absence, the bill is now on hold.

The other major legislation on hold is a 1,000-page overhaul of the Higher Education Act, which sets policy for colleges and universities as well as federal financial aid rules. The legislation has been the subject of tense negotiations between the House and the Senate, and the two chambers were debating how to deal with textbook costs and other prevailing problems in higher education funding.

A House-Senate conference has been postponed in Kennedy’s absence.

And in the health care realm, a major Kennedy bill to encourage use of electronic medical records was moving toward completion. It is unclear whether Kennedy will return in time to manage that bill.